Study on magnetic excitons in uranium-based heavy fermion superconductors

铀基重费米子超导体中磁激子的研究

• 批准号: 12440091
• 负责人: SATO Noriaki
• 金额: $ 7.3万
• 依托单位: Nagoya University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (B)
• 财政年份: 2000
• 资助国家: 日本
• 起止时间: 2000 至 2002
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-12440091/
• 关键词: uranium compounds; heavy fermions; superconductivity; magnetic exciton; UPd_2Al_3; UNi_2Al_3; UGe_2; URu_2Si_2; UNi_2Ai_3

(1) Magnetic exciton mediated superconductivity in UPd_2Al_3We succeeded in preparing single crystals of high quality, and measured physical properties of those crystals to obtain information of the magnetism and superconductivity. We discovered the existence of two components in inelastic neutron scattering spectra, and we safely ascribed the lower energy component to quasiparticle excitations and the higher energy one to magnetic excitons. We proposed a new model, that is called "dual nature of 5f electrons", to analyze the data. We finally found the strong coupling between the two components. We also found that the spectra are consistent with spectra obtained from tunneling experiments within the Eliashberg equation framework. From these results, we pointed out that the superconducting attractive interaction is mediated by exchange of bosonic magnetic excitons. This result was reported in Nature, 410(2001)340-343.(2) Magnetism and superconductivity in UNi_2Al_3In UNi_2Al_3 that has … More the same crystal structure as UPd_2Al_3, the antiferromagnetic ordered state also coexists with superconductivity. We carried out NMR experiments, and found that the Knight shift shows no reduction below the superconducting transition temperature, in remarkably contrast with the isotropic reduction in UPd_2Al_3. From this result together with the absence of the Pauli limiting effect in the temperature dependence of the superconducting upper critical field, we concluded that the spin-triplet (odd parity) paring is formed.(3) Magnetism and superconductivity in UGe_2 and URu_2Si_2We prepared single crystals to investigate the correlation of ferromagnetism and superconductivity in UGe_2. We measured the dc magnetization and ac magnetic susceptibility under high pressures, and we found that the superconducting volume fraction grows with increasing pressure. From this, we suggested that the superconductivity coexists in a competitive way with the ferromagnetism.We also carried out the dilatation measurements under high pressure for single crystals of URu_2Si_2. We found an anomaly in the thermal expansion coefficient that corresponds to the phase transition between hidden and antiferromagnetic order. Less

项目成果

K.Ishida, N.K.Sato, N.Aso, C.Geibel, F.Steglich 他: "Spin-triplet superconductivity in UNi_2Al_3 revealed by the ^<27>Al Knight shift measurement"Phys. Rev. Lett.. 89. 037002-1-037002-4 (2002)

K.Ishida、N.K.Sato、N.Aso、C.Geibel、F.Steglich 等人：“^ 27 Al Knight 位移测量揭示了 UNi_2Al_3 中的自旋三重态超导性”Phys。 037002-1-037002-4 (2002)

T.Nishioka, G.Motoyama, S.Nakamura, H.Kadoya, N.K.Sato: "Unusual nature of ferromagnetism coexisting with superconductivity in UGe_2"Phys. Rev. Lett.. 88. 237203-1-237203-4 (2002)

T.Nishioka、G.Motoyama、S.Nakamura、H.Kadoya、N.K.Sato：“铁磁性与 UGe_2 中超导性共存的不寻常性质”Phys。

N.K.Sato: "Magnetism and superconductivity in UT_2Al_3 (T=Pd, Ni) and UGe_2"Physica C (Proceedings of LT23, Hiroshima, 2002). (印刷中). (2003)

N.K.Sato：“UT_2Al_3 (T=Pd, Ni) 和 UGe_2 中的磁性和超导性”Physica C（LT23 会议记录，广岛，2002 年）（出版中）。

A.Hiess, N.K.Sato: "Neutron scattering study of the static and dynamic magnetic properties of UNi_2Al_3"J.Magn.Magn.Mater.. 226-230. 54-56 (2001)

A.Hiess、N.K.Sato：“UNi_2Al_3 静态和动态磁性的中子散射研究”J.Magn.Magn.Mater.. 226-230。

A.Hiess, P.J.Brown, E.Lelievre-Berna, N.Aso, N.K.Sato et al.: "Spherical neutron polarimetry of the magnetic structure in UNi_2Al_3"Phys. Rev. B. 64. 134413-1-4 (2001)

A.Hiess、P.J.Brown、E.Lelievre-Berna、N.Aso、N.K.Sato 等人：“UNi_2Al_3 中磁性结构的球形中子极化测量”Phys。